The invention relates to a novel means and mechanism for maintaining air pressure in pneumatic tires of motor vehicles, such as automobiles and trucks, and more particularly to such a novel device which automatically maintains a desired and predetermined tire pressure. The apparatus of the present invention for automatically pressurizing and regulating pneumatic tires is attachable to a vehicle wheel and is operated by the rolling motion thereof.
Numerous tire pressurizing and regulating apparatus for motor vehicle wheels have been invented and/or previously developed. However, they tend to be expensive to manufacture and/or inefficient in operation.
In U.S. Pat. No. 1,127,079, Nielsen illustrates a pendulum operated air compressor which is mounted on a wheel to automatically inflate a pneumatic tire mounted on a wheel. While the basic concept disclosed is meritorious, nevertheless, the apparatus is impractical by today's standards, cumbersome, expensive to manufacture and inefficient in operation. The linkage utilized to operate the compressor from the pendulum is a crank-arm mechanism which cannot efficiently operate and causes the wheel to rotate in an unbalanced condition, which is not acceptable for modem fast moving vehicles. In addition, the pendulum mechanism itself is exposed to the elements and therefore subject to interference and contamination by dirt, snow, etc.
In U.S. Pat. No. 5,342,177, Cheng illustrates an automatic pneumatic pump which also uses a cylinder and piston assembly which rotates with the wheel and the pneumatic tire mounted on the wheel. The piston is reciprocated by contact with a stationary cam to provide pressurized air to the tire. The stationary cam is secured with the stationary bicycle axle. This pneumatic pump assembly is meritorious in that a relatively efficient cam mechanism is utilized to operate the pump, instead of the cumbersome assembly illustrated in Nielsen.
Major problems with the Cheng automatic pneumatic pump device are that it is not readily adaptable to use on a motorized vehicle such as an automobile or truck. In addition, Cheng's pump construction requires that his cylinder and piston assembly must rotate off center with the wheel and by necessity also provide a camming action which imparts a camming thrust radially outward from the wheel axle. The combination of these requirements is that the wheel is caused to be measurably unbalanced, which is intolerable for fast moving motor vehicle wheels, even though it may be acceptable for bicycle wheels. This unbalanced condition also adds to wear and tear on the pump mechanism.
U.S. Pat. Nos. 1,744,405 and 2,415,618 are respectively issued to West and McCord and illustrate pendulum operated air pumps for automatically inflating vehicle pneumatic tires. These pumps are greatly simplified from the prior art pendulum pump illustrated in Nielsen, but have some of the same short comings.
Again, the piston cylinder combinations utilized in West and in McCord, are of a construction which requires that the entire cylinder and piston assembly must rotate off center about the axis of rotation of the wheel, thereby requiring the pump to operate and the wheel to operate in an unbalanced condition. Also the camming mechanisms create additional unbalancing forces which are applied adversely to the rotating wheels.
Other problems encountered with all of the aforementioned prior art structures are that their exhaust or outlet check valves utilized in their piston-cylinder combinations are very much adversely affected by centrifugal forces. As the respective wheels of the prior art devices rotate faster, increased centrifugal force is imparted to the respective outlet check valves of the prior art pumps. Accordingly, with all of the prior art pumps, the air pressure being exhausted from the respective pumps varies tremendously in accordance with the rotation velocity of the wheel to which the pump is attached. The spring loaded outlet valves can therefore not be utilized for or relied upon to regulate air pressure to the pneumatic fire, and at higher wheel velocities will not provide adequate air pressure due to the leaking of the valves created by the applied centrifugal force. Accordingly, with the prior art pumps, a higher pump pressure or differential pressure must be provided in order to effectively operate them, and this in turn requires costlier manufacturing techniques.
Additionally, all of these pendulum operated pumps of the prior art teach the use of conventional piston and cylinder combinations wherein the compression and intake or retraction strokes are equal in velocity. In other words, the piston compression strokes of the prior art pumps are relatively slow and therefore require exacting tolerances in piston and cylinder fit, thereby making the prior art pumps less efficient due to the frictional engagement and of greater mass than desired to house the tight tolerance fitting piston and cylinder combination.
It is a principal object of the present invention to provide a pendulum operated pump for harnessing and utilizing the rotational forces of a vehicle wheel for pressurizing and regulating the pressure of a pneumatic tire carried by the wheel with a pump mechanism which is inexpensive to manufacture and efficient and balanced in operation.